Pressure welding machine



Feb. 12, 1952 R. T. MURRAY EI'AL 2,585,266

PRESSURE WELDING MACHINE Filed Sept. 27, 1946 2 SI-IEETSSHEET l I N V ENTO R5 7.' MURRH Y Fl OHM/00 VI T/ ATTORNEY Feb. 12, 1952 R. T. MURRAYETAL PRESSURE WELDING MACHINE 2 SHEETSSHEET 2 Filed Sept. 27, 1946\NVENTORS RU5$ELL 7: MURRAY BY FLOR/N00 V/T/ ATTORNEY Patented Feb. 12,1952 TENT OFFICE PRESSURE WELDING MACHINE Russell '1". Murray, ElCerrito, and Florindo Viti,

San Francisco, Calif., assignors to Grove Regulator Company, Oakland,Calif., a corporation of California Application September 27, 194-6,-Serial No. 699,858

7 Claims.

This invention relates generally to machines suitable for carrying outpressure welding operations;

So-called pressure welding as practiced in many metal fabricatingoperations makes use of a hydraulic press which receives the metal partsto be welded together, and which-is capable'of applying relatively highforce to the jointto be welded, while heat is being applied. As themetal softens the operator supplies additional liquid tothe hydrauliccylinder'of the press to cause the metal parts to advance together apredetermined distance.

Pressure welding has been found. critical to many factors of the method,including particularly application of the necessary force between theparts being welded both during the initial part of the heating cycle andwhile the parts are being advanced together. Variations in the appliedforce make for erratic and unsatisfactory results.

It has been found that hydraulic presses of the type heretofore used forpressure welding are not capable of producing and maintaining forceswithin the limits of accuracy desired. This is attributed to frictionbetween the piston and cylinder, to leakage from the hydraulic system,and to the manner in which it is attempted to control application ofliquid to the cylinderpiston assembly.

It'is an object of the present invention to provide an improved pressurewelding, machine capable of accurate and automaticcontrol of the forcesapplied.

A further object of the invention is to provide a machine of the abovecharacter which will not only maintain the desired force upon the partsbeing welded prior to heating, but which will also" advance the partstogether when the metal is softened with continued automatic control ofthe applied pressure.

Additional objects of the invention will appear from the followingdescription in which the preferred embodiment has been set forth in.detail in conjunction with the accompanying drawing.

Referring to the drawing:

Figure 1 is a side elevational view diagrammatically illustrating amachine incorporating the present invention.

Figure 2 is an enlarged cross sectional detail illustrating theauxiliary pneumatic assembly used with the hydraulic cylinder-pistonassembly.

Figure 3 is an enlarged detail in section showing the'pneum'atic controlvalve.

The machin as schematically illustrated in V 2- Figure 1- consists ofaframe 10 which serves to support the hydraulic cylinder-piston assemblyH. The force transmitting rod or ram H extends fromone end of thisassembly and is movable in opposite directions dependent upon theapplication of liquid to the cylinder. Instead of applying force.directly from ram l2 to the parts to be. welded, the ram isattached to apneumatic device 43; which in turn carries a force applying head M. Anadditional head I6 is used in conjunction With-head l4. andis suitablymounted in stationary position. upon the main frame or bed til of'themachine. The main body. of device 53 is shown supported by a bracket H,which in turn is slidably carried by the horizontal ways IS.

The heads I l and I5 are suitably formed and adapted to apply pressureto the particular metal parts whichare to be pressure welded. By way ofexample head I6 is shown provided with clamping means I 9 for engagingan end flange on thehollow annular part 2|. Part 2| is to be pressurewelded to a hollow annular part 22, whichv in turn abuts the adjacentface of head M; I, As is wellknown to those familiar with pressurewelding the adjacent end faces of parts 2| and 22 are suitably beveledand adapted to be brought together in proper alignment preparatory tothe welding operation. The region to be pressure welded isshow'n beingsurrounded by the ring-like torch 23, which can be suitably support'edbythehorizontally movable carriage 24.

The hydraulic system for supplying liquid under pressure-to thecylinder-piston assembly H includes a constant displacement liquid pump26 having its inlet connected to the lower portion of the liquid supplytank 21. The discharge side of the pump connects with pipe 28 whichleads to. the spring. loaded pressure relief valve 29. Pipe 3| connectswith the relief or venting port of the valve 19, and leads back to thetank 21. Pipe 32 connects with the body of valve 29 and leads to amultiport valve 33. This valve is preferably of the slide type and isoperated by two electrical solenoids 3 3, 36. One pipe 35 conmeets withvalve 33 and leads back to the tank 21. Pipes 3'! and 38 connect betweenthe valve 33 and the four way hand control valve 39. Pipe 4! connectsbetween this valve and one end of the cylinder-piston assembly I l, andthe pipe 42 connects between valve 39 and the other end ofthesameassembly.

Suitable electrical circuits 43 and 44 connect with the solenoids 34,36. supplied with current from a suitable source such area step'downtransformer 46. Circuit 43 in- Both circuits are 3 cludes the seriesswitches 41 and 48, and circuit 44 includes the series switch 49.Assuming that circuit 43 has last been energized, then liquid underpressure is supplied from pump 25 through the slide valve 33 to the pipe31. The liquid from pipe 31, in turn is supplied to pipe 4| whereby theram I2 is moved to the right as viewed in Figure 1. For anotheroperating position of valve 33 liquid is supplied to pipes 38 and 42 andis vented from pipe 4|, whereby the ram I 2 is moved to the left. Valve39 can be placed in intermediate throttling positions to control thespeed of movement of the ram.

In order to control the pressure of liquid supplied to pipe 4| weprovide a pressure relief regulator 59. Pipe 5| connects the inlet portof this regulator to the pipe 4|, and pipe 52 connects the dischargeside back to the tank 21. The valve member of this regulator is operatedby a suitable diaphragm assembly 53, and the diaphragm in turn is loadedby application of gas under pressure. Relief regulators of this type areknown to those skilled in the art. With continuous supply of liquid fromthe pump 26 to line 4|, regulator 50 is set to continuously bypassliquid back to the tank 27 through pipe 52, with the rate of returnbeing automatically adjusted to maintain a given pressure, which in turnis determined by the pressure of gas supplied to the diaphragm assembly53.

A special automatically controlled pneumatic system is provided forcontrolling the loading of the relief regulator 50. Thus pressurereducing regulators 55 and 51 are provided and are supplied with airunder pressure through the supply line 58. It is desirable that theseregulators be capable of adjustment over a relatively wide range ofoutlet pressures, and for this purpose we have used with good results aregulator of the type disclosed in Patent No. 2,342,659. Differentloading springs are used on the two regulators so that by using eitherone or the other regulator a relatively wide range of reduced pressurescan be supplied. For example regulator 56 can supply reduced pressuresup to 160 p. s. i., and regulator 51 pressures from 160 p. s. i. to 900p. s. i. The outlet sides of these regulators are shown connected withsuitable pressure gauges 59, '60, and hand operated valves GI and 62 areprovided for shutting off one or the other regulator. Pipe 63 leads fromthe regulators 56, 51 to the solenoid operated vent valve 64, which inturn is connected by pipe 66 to the body of device I3.

An additional pressure reducing regulator 61 is provided, and the lowpressure side of this regulator is connected by pipe 68 to a controlvalve 69. Valve 69 is of the supply and waste type, and one of its portsis connected by pipe II to the pressure chamber of the diaphragmassembly 53 (regulator 50).

The solenoid of valve 64 is shown connected to the energizing circuitI2, which includes in series with the same the electrical switch I3.This switch is operated by engagement with the cam I4, as will bepresently explained. The contacts of switch "I3 can be connected inshunt with switch 4'! as indicated by dotted lines.

The pneumatic device I3 includes relatively movable parts adapted to beurged apart by application of pneumatic pressure. A desirableconstruction is illustrated in Figure 2. The device in this instanceconsists of a main body 8| which 18 annularly contoured and adapted tobe, rigidly attached to the adjacent end 01' the hydljaulic ISO ram I2.The body is provided with an inner cylinder bore 82 within which isfitted the ringlike piston 83. The periphery of this piston is sealedwith respect to the adjacent walls of the bore 82 by suitable means suchas the resilient O ring 84. Piston B3 in turn provides an inner cylinderbore 86.within which is fitted a secondary piston 81. A suitable meanssuch as a ball bearing assembly 88 maintains alignment between parts 83and 81 and permits relative axial movement between the same with aminimum of friction. Leakage between parts 83 and 81 is prevented bysuitable means such as the resilient O ring 89.

The secondary piston 81 also has an axial bore 9| serving to accommodatethe ball bearing assembly 92. Fitted within this assembly there is astud 93 which has an extension 94 fitted within a bore 96, formed in thebody. Extension 94 is sealed with respect to the body by suitable meanssuch as the resilient O' ring 91. Stud 93 serves to support secondarypiston 81 for limited axial movement relative to the body, while thesecondary piston in turn, through the ball bearing assembly 88, servesto support the piston 83 for movement with a minimum of friction.

The main cylinder bore 82 of the body BI is enclosed by the cover plateIBI which has a central opening I02 for receiving the cylindrical shapedthrust transmitting member I03. This member is rigidly mounted on headI4 and is retained by screw I05. The periphery of member I03 engages theball bearing assembly I04, and its inner portion is provided with aflange I08. Circumferentially spaced set screws I01 are threadedinto thecover plate IN, and the inner ends of these screws are adapted to bearagainst the adjacent face of the piston 83. It can be explained at thispoint that when screws I01 are turned to bear upon the piston 83, thispiston is retained stationary and is not permitted to contact the innerend of thrust transmitting member I03. Thus the piston 81 is the onlyone effective for transmitting thrust to the member I03. when set screwsI01 are turned to retract the same from thepiston 83, both pistons 83and 81 are permitted to move in unison, and therefore the effectivefluid pressure provided is greatly increased. The arrangement justdescribed is desirable to adapt the machine over a wide range of forcesto be applied, thus making the machine better adaptable for differentsized parts to be pressure welded.

Thrust transmitting member I03 is directly at tached to the head I4 asby means of the screw I05. The head is shown provided with a stud- 2slidably accommodated within an opening H3 at one edge of the coverplate IIII, in order to prevent relative rotation of the head withrespect to the body 8 I.

The pilot control valve 69 is conveniently mounted upon the body 8| ofthe pneumatic device I3. As illustrated this valve may consist of amovable part II3 accommodated within the bore I I6, and provided withthe two valve elements H1, H8. These valve elements cooperaterespectively with stationary seats H9 and I2I. Supply pipe 68 connectswith the inlet passage I22, and pipe connects to the duct through thepassage I23, which communicates with the: opening H6. The valve part 4is attached to an operating stem I24 which extends loosely through theretaining. fitting I26. When stem I24 is moved-to the left as viewed inFigure 3, (it is normally urged to the right by pneumatic assumespressure), there is a: throttling of communication betweenpassages I23and I 22; and simultaneously there is: some venting of air to the:atmospherethrough the space about stem 1'24. When stem [2 34's moved toitslimiting left hand" position as viewed in Figure 3, all'supply of airto. the passage [22 is interrupted and there is complete venting of airtothe atmosphere. a

To eitectoperation of the stem. I24 we provide a pin I 3! which isslidably retained within the screw I321 Compression spring I33 normallyurges: pin I31" to its limiting left hand position asviewe'd in Figure2. Screw I32 is shown thread.-

within: a split tab 34, which is carried by the upper edgerof tl-ie head14'. With the arrangement.

just: described it is evident that when head it moves a small amount tothe left as shown in Figure 2; pin l3'lis brought into engagement withstem I24 whereby the stem IN is moved to the left to effect: a.controlled venting of air. to the atmosphere and to control. supply ofair to the valve passage I22 andpipe 68.

Operation of the machine described above is as follows: The two arts.21. and: 22 to be pressure welded together; after suitable preparation.of their end faces, are loaded intothe machine substantially asillustrated. At the same time the torch Z3. is positioned to surroundthe zone to beweld'ed together. The torchis connected to a suitablesource of. acetylene and oxygen gas,

through suitable pressure. reducing regulators-and mixers; If desired anadditional internal torch canbe-provided for the purpose of heating fromwithin simultaneously with. external heating.

Either one of the pressure reducing regulators 5G or 5'! is selected foruse, depending upon the size of work being welded. Assuming for examplethat. one desires to supply apressure of 500 p.. s. i. to pipe 66: anddevice 13, then pressure reducing regulator 51 is selected and adjustedaccordingly. Assumingthat one uses the. total effective fluid pressureof both pistons 83. and. 81 of; device I3; then. both of these pistonsare urged totheir right hand limiting positions (Figure 2.) and theheadIt cannot move relativeto the body 8| except upon application of forcesufficient to balance the pneumatic pressure. Assuming aplication of apneumatic pressure of the order of 500p. s. i. the force required tobalance the same may for example be the order of 40,000 lbs.

Throughout operation of the machine until the weld is completed, thisfluid pressure is appliedcontinuously to the device [3. Pressurereducing regulator 61 is set to supply an outlet pressure consistentwith the loading pressure requirements of the relief regulator 50. In atypical instancethis may for. example be of the, order of 50p. s.- i.Spring loaded relief regulator 29 is set for a somewhat higher pressurethan regulator 50. Assuming that. pump 26' placed in continuousoperation and switch 73, closed, the button switch 48 is closedmomentarily'toenergize the solenoid 34, with the result that liquid frompipe 32 is applied through pipes 37 and 4'!" whereby'the' ram I2 ismoved to the right to supply the desired pressure upon the work, Asthe'pressure upon the work reaches the desired value for which themachine: is set the pneumatic device l3 reaches balanced'condition and asmall amount of relative movement occurs between the body SI of thisdevice and the head Mi Such movement brings the pin 131 into operativeengagement with the stem I24 of the control valve 69, with the resultthat air is vented past the valve element H8, whil valve element ll!increases the restriction between passages iii-and l22 (Eigure3). Asaresult the pressure in passage I23. and pip H is effectively reduced,and, thisin. turn changes the loading upon the relief regulator 50 tocause this regulator to by-pass liquid back to the tank 2]. Thus uponattaining a conditionv of equilibrium all of the liquid from the pump 26is icy-passed byregulator 5i v back to the tank, and automatic controlof this regulator maintains the liquidpressure applied to pipe 41 and tothe cylinderto produce the desired force upon the work.

Gas supplied to the torch 23 is ignited and the abutting: portions ofthe parts 21, 22, rapidly heated to the-point: oiplasticity.Uponreaching a condition. of plasticity the pneumatic pressure in device[3 causesv some additional advancing movementxo fithe. head. M, with theresult thatthe control valve 69 is operated in the manner previouslydescribed to increase the loading upon the relief. regulator 50, therebyin turn increasing'the supply of liquid. through pipe 4! to themaincylin den. The hydraulic ram l2 together with device [3 and head 14are now advanced forwardly a predetermined distance sufficient toproduce the wel'ddesi-red.

Advancing movement of the head l4 isarrested by automatic means, such asa cam 14 and switch '3. Cam i4 is carried. by the head l4, and switch:13 located on a stationary support whereby when the desired amount ofadvancing movement'has taken place cam i l operates. switch. 13. toclose its contacts; This causes operation of the solenoidvalve as, withthe result that air is-vented frcm pipe us, to reduce-the pneumaticpressure applied to: device: l3. to atmospheric; Such venting resultsin. movement of the body 8| until all of: the motion between this bodyand head l4 is-taken up, at which time pin I3! has moved the valvemember M4 to its limitin position, in which communication betweenpassages I22iand' 523* iscompletely interrupted, and passage I23 vented.to the atmosphere. Thus loading upon the relief regulator 5'0is reducedto substantially atmospheric. At the same time that the: solenoid valve64 is operated by closing of switch 73, there is simultaneousoperationof the solenoid 34 tocompletely cut off further supply ofliquid to themastercylinder. Likewise switch I3 may energize anothercircuit (not shown) for the purpose of operating a solenoid valve to out01f supply'ofgas to the torch 2:3. The softened portions of the parts 21and 22- solidify almost instantaneously, and vth'ese welded parts cannow be removed from the machine, after removal of the torch 23. Byoperation of switch button valve 3 3 is operated to apply liquid to pipe38 rather" than pipe 31; and topermit liquid from pipe 5&1 to ventthrough pipe'35 to the tank 21. This in turn serves to vent liquidthrough pipe 413 iromthe-master-cylinder, and to apply liquid to pipe:42. The setting'of regulator at thistime aii'ords sufficient pressurewhich when applied through pipe 41, serves to return the rain ['2 to itsinitial position.

It will-beevi'dent from the foregoing that our machine possesses manyadvantages over the use of simple hydraulic presses for pressure weldingThe force to be applied to the parts being welded together can be moreaccurately controlled. and when set for a given value, thesame force isobtained for'successive operations to produce consistent welding resultson a production basis. The force applied to the work is made independentof friction between the moving parts,

particularly having reference to friction between the hydraulic pistonand its associated cylinder. In addition to obtaining the desired forceupon the parts to be welded during the initial part of the heatingcycle, the parts are forced together upon the metal reaching the plasticstate in such a manner as to produce a good pressure weld, and withcontinued application of the force required for the upsetting operation.In addition to the features mentioned our machine is relatively simpleto operate, and to adjust for different types of work.

We claim:

1. In a machine for butt pressure welding operations of the type inwhich abutting parts to be welded are urged together, flash heated, andthen forced together to complete a weld, a hydraulic cylinder-pistonassembly, means for sup plying liquid under pressure to said assembly, apneumatic cylinder-piston assembly, said last named assembly beingarranged to transmit force from the first assembly to the abutting metalparts to be welded, means for supplying gas under pressure to said lastnamed assembly whereby for a given pneumatic pressure applied thecylinder and piston of the pneumatic assembly will be in balancedcondition for a given force being applied to the metal parts beingwelded, a pneumatic control valve of the supply and waste type operatedresponsive to relative movements between the cylinder and piston of thepneumatic assembly, a source of air under pressure connected to saidvalve, a gas pressure loaded relief regulator adapted to control thesupply of liquid to the first named assembly, and a pneumatic connectionbetween said last named valve and said control valve whereby thepressure of liquid supplied to the hydraulic cylinder-piston assembly iscontrolled in response to relative movement between the cylinder andpiston of the pneumatic assembly.

2. In a machine for butt pressure welding operations of the type inwhich abutting parts to be welded are urged together, flash heated, andthen forced together to complete a weld, means adapted to apply force tometal parts being pressure welded, means for applying heat to said partsin the region of the welding zone, and means serving to continueapplication of force as the two parts being welded advance together atthe end of the heating cycle, said means functioning responsive torelative movement between the metal parts in a direction toward eachother.

3. In a machine as in claim 2 in which means is provided to limitadvancement of the two parts together.

4. In a machine for butt welding operations, a frame, working headscarried by the frame and between which parts to be butt welded may beplaced, one of said heads being mounted stationary on the frame, ahydraulic cylinder carried by the frame, a movable hydraulicallyoperated ram extending from the cylinder, a source of liquid underpressure for the cylinder, a device for controlling supply of liquid tothe cylinder from said source, a pneumatic cylinder carried by the ram,a piston fitted in said cylinder and attached to said other head, asource of air under pressure connected to said pneumatic cylinder, andmeans for controlling the presure of liquid supplied from said source tosaid cylinder in accordance with relative movement between said otherworking head and the ram.

5. A machine as in claim 4 in which said last named means comprises avalve of the supply and waste type actuated by relative movement of saidother working head relative to the ram.

6. In a machine for butt welding operations, a frame, working headscarried by the frame and between which parts to be butt welded may beplaced, one of said heads being mounted stationary on the frame, ahydraulic cylinder carried by the frame, a movable ram extending fromthe cylinder, a source of liquid under pressure for the cylinder,pneumatic pressure loaded regulating means for controlling the pressureof liquid supplied from said source to said cylinder, a pneumaticcylinder carried by the ram, a piston fitted in said cylinder andattached to said workhead, said ram together with said pneumaticcylinder and said piston being in alignment, a source of air ofpredetermined pressure connected to said pneumatic cylinder, and meansfor controlling the pressure of liquid supplied from said source to saidcylinder in accordance with relative movement between said other workinghead and the ram, said means comprising a source of air under pressure,valve means of the supply and waste type connected to said source of airpressure, a connection between said valve means and said regulatingmeans whereby the pressure of air supplied to said regulating meansdetermines the loading of the same and the pressure of liquid suppliedto said cylinder, and means for operating said valve means responsive torelative movement between said other working head and said ram, therebycausing the pneumatic piston to assume a balanced position with respectto the ram for application of a predetermined force to the parts to bewelded.

7. In a machine for butt pressure welding operations, hydraulic meansadapted to apply force in response to supply of liquid under pressure tothe same, relatively movable members providing a closed chamberinterposed between the hydraulic means and the abutting metal parts tobe welded, whereby force from the hydraulic means is transmitted throughsaid members, said RUSSELL T. MURRAY. FLORINDO VITI.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,764,098 Galloway June 17, 19302,146,537 Farnham Feb. 7, 1939 2,374,577 Bench et a1. Apr. 24, 19452,392,824

Lytle et al. Jan. 15, 1946

